There are two important compenents of MapReduce.

    JobTracker
    TaskTracker

JobTracker Functions

    Acts like a Resource Manager

    Keeps a track of All Tasktrackers

    Schedules Jobs.

    Informs TaksTracker, what jobs need to be run

    JobTracker knows the status of all the Tasktrackers

TaskTracker Functions

    Periodically Updates JobTracker

    Runs Task

    Interacts with the HDFS and executes tasks